In-mold labeling has been developed in the recent past to provide superior bonding of labels to blow molded containers. Such in-mold labeling is performed by inserting a label within an open mold prior to closing of the mold around an extruded hot plastic tube or a heated injection molded plastic preform. Subsequent mold closing and blow molding forms the hot plastic around the label to the shape of the mold and activates a heat sensitive adhesive that provides a permanent bond which is incapable of being broken by moisture or otherwise. Also, such in-mold labeling provides a smooth transition between the label and the adjacent surface of the container and further provides additional strength since the label cooperates with the container wall in resisting deformation. Such strengthening also allows the use of less plastic to blow mold the container and thereby reduces the ultimate cost to the consumer. Furthermore, when utilized with containers for carbonated beverages, the in-mold labeling reduces the flow of carbon dioxide out through the container wall over a period of time and thereby increases the shelf life.
U.S. Pat. No. 4,479,770 Slat et al., 4,582,474 Ziegler, 4,639,207 Slat et al., and 4,909,723 Slat et al. disclose in-mold labeling systems wherein a dispensing head of the in-mold labeling system is moved between a label supply location aligned with one or more label magazines adjacent the associated blow molding machine and a label delivery position within an adjacent open mold of the blow molding machine, and one or more label carriers on the dispensing head is moved between a retracted position and a label transfer position in order to provide a pick and place movement of the labels from the label magazines into the mold where a vacuum is drawn to secure the label to the mold before mold closing for the blow molding operation. A vacuum is also utilized by the label carrier to secure the labels for the movement from the associated label magazine to the associated mold.
In-mold labeling systems of the type described above have previously included a common mechanical drive from the blow molding machine for driving the dispensing head between the label supply and delivery locations and for also driving the label carriers between the retracted and label transfer positions. As such, the respective speeds and movements of the dispensing head and each label carrier are coupled with each other.
With relatively high speed labeling, it has been found that it is difficult to remove labels from a label magazine at a greater speed than about 65 to 70 labels per minute since such high speed operation does not allow time for air to enter behind the label as the label carrier pulls it from the label magazine. As such, more than one label can be pulled away and thereby cause problems in the in-mold labeling process.
Previously, in-mold labeling of a pair of labels to an associated pair of mold members of a mold has been performed in two ways. In one practice, a pair of rotary drive members that are spaced from each other and each rotates an associated lever that has a cam and follower connection to an associated label carrier to provide the label carrier movement between the retracted and label transfer positions. In another practice, a single rotary drive member is utilized and through a lever drives one label carrier that is connected by a gear and rack assembly to another label carrier so that both label carriers are concomitantly moved between the retracted and label transfer positions by the rotation of the one rotary drive member.
Other United States patents disclosing in-mold labeling for plastic blow molding include: 4,680,000 Nowicki et al.; 4,729,731 Hasl et al.; 4,801,260 Oles et al.; 4,808,366 Kaminski et al.; 4,834,641 Keyser; 4,861,542 Oles et al.; 4,880,368 Hasl et al.; 4,944,665 Hasl et al.; 4,973,241 Keyser; 5,044,922 Plenzler et al.; 5,086,937 Robinson; 5,169,653 Tate et al.; 5,192,554 Savich et al.; 5,275,780 Robinson; 5,344,305 McKillip; 5,350,483 Yager et al.; 5,383,779 Robinson; 5,665,404 Weber et al.; 5,753,278 Aguilar; and 5,759,593 Weber et al.